Rechargeable battery packs, especially the type designed for power tools such as drills, saws and sanders have become common place. The battery packs can come in different voltages and current ratings and may be interchangeable with other battery packs, such that when the charge from one is exhausted, another charges battery pack can be used. The battery powered tools are particularly useful for new construction where power has not been installed yet, situations where the power is out and remote locations where power is not available.